This invention relates to the demulsification of crude oil to separate water from the oil. More specifically, the invention is an emulsion polymer soluble in the dispersed water naturally present in a crude oil flowing from the well head.
Chemical demulsification has since long established itself as the cheapest, most convenient and effective method in breaking a water in crude oil (w/o) emulsion. Demulsification has gained in importance because the use of steam and caustic injection or combustion processes, for in-situ recovery of heavy oils, is complicated by the production of viscous emulsions of oil, water and clay. Crude oil is found in the reservoir in association with gas and saline formation water. As the reservoir becomes depleted a time will be reached when water is coproduced with oil. The number of wells now coproducing water with crude oil is steadily increasing; these immiscible fluids are readily emulsified by the simultaneous action of shear and pressure drop at the well head, chokes and valves.
It has long been recognized that the resulting w/o emulsion can be remarkably stable. Further, it is now understood that indigenous crude oil surfactants adsorb at the oil-water interface giving rise to a physically strong film, an interfacial skin around the dispersed water droplet, which in turn promotes these stable emulsions. The coproduction of the water with crude oil may give rise to a variety of problems. These include the expense of pumping or transporting water via pipeline or tanker; the corrosion of pipework, pumps, production equipment and downstream overhead distillation columns and the poisoning of downwstream refinery catalysts. Consequently, those factors which either enhance or reduce crude oil emulsion stability are of considerable importrance to the oil industry.
Oil soluble demulsifiers are commonly used to destabilize the w/o emulsions. These emulsions are moderate (2,000-50,000) molecular weight, polydispersed interfacially active polymers. They are mostly non-ionic block polymers with hydrophilic and hydrophobic segments. The method of production of oil soluble demulsifiers in most cases involves handling of dangerous and expensive chemicals like ethylene and propylene oxide. It would be highly desirable to have demulsifiers that are water soluble but as effective as their oil soluble counterpart. The primary object of this invention is to achieve such a water soluble demulsifier.